Mortality Attributable to Ambient Fine Particulate\nMatter Exposure in a Changing Canadian Population, 2001 to 2021

We aim to understand\nhow changes in ambient fine particulate matter\n(PM<sub>2.5</sub>) over the last two decades have influenced PM<sub>2.5</sub>-attributable mortality in a Canadian population experiencing\nboth growth and changing baseline health status. We conducted a health\nimpact analysis using dynamic estimates of population, baseline mortality\nrates, and satellite-based PM<sub>2.5</sub> concentrations to estimate\nmortality attributable to long-term PM<sub>2.5</sub> exposure every\nfive years between 2001 and 2021, applying risk estimates from the\n2006 Canadian Census Health and Environment Cohort (CanCHEC) to the\npopulation aged 25 and older. We conducted a decomposition analysis\nto examine the influences of population exposure, size, and health\nstatus on trends in PM<sub>2.5</sub>-attributable mortality. Between\n2001 and 2021, population-weighted exposure to PM<sub>2.5</sub> declined\nby 18% in Canada, with improvements occurring in most urban areas.\nIn recent years, these changes have led to 4,400 (95% CI: 3,700–5,000)\nto 4,700 (95% CI: 4,100–5,400) fewer PM<sub>2.5</sub>-attributable\ndeaths annually based on log–linear and log–log shapes\nof concentration–response. However, a growing population alongside\nhigher baseline mortality risks in several regions, likely due to\naging, has led to a small net increase in total PM<sub>2.5</sub>-attributable\ndeaths between 2001 and 2021. These findings suggest that the Canadian\npopulation has benefitted broadly from air quality management strategies\nimplemented in North America over recent decades.